title: Correlation of radiographic signs, inferior dental nerve exposure, and deficit in third molar surgery.
abstract: OBJECTIVE
  To identify the specific radiographic signs on orthopantomograms that are positive predictors of intraoperative inferior dental nerve (IDN) exposure and postoperative IDN deficit in lower third molar surgery.
  
  
  METHODS
  A prospective clinical cohort of patients with lower third molars with specific radiographic signs showing a close proximity of the roots to the IDN who underwent total excision at our center from June 2006 to June 2008 were recruited as the study group. The prevalence of intraoperative IDN exposure and postoperative IDN deficit were recorded. The correlations between the various radiographic signs and the prevalence of IDN exposure and deficit were analyzed. The prevalence of IDN deficit in the sample was compared with an age-, gender-, and operator experience-matched control group of patients who had undergone lower third molar surgery without any of the radiographic signs present.
  
  
  RESULTS
  Patients with a total of 178 lower third molars with 1 or more of the specific radiographic signs present were recruited as the study group. The prevalence of IDN deficit in the study group (5.1%) was significantly greater than that in the control group (0.56%; P = .01). In the study group, darkening of root and displacement of the inferior dental canal by the root were radiographic signs significantly related to IDN exposure (P = .001 and P = .019, respectively). Darkening of the root was the only sign significantly related to a postoperative IDN deficit (P = .016). When 2 or more radiographic signs were present, the risk of a postoperative IDN deficit was significantly increased (P = .001).
  
  
  CONCLUSIONS
  Darkening of the root and displacement of the inferior dental canal by the root were positive predictors of intraoperative IDN exposure. Darkening of the root or the presence of 2 or more radiographic signs were positive predictors of a postoperative IDN deficit.
authors.affiliation: Discipline of Oral and Maxillofacial Surgery, Faculty of Dentistry, The University of Hong Kong, Hong Kong, People's Republic of China.
authors.forename: Yiu Yan
authors.initials: YY
authors.lastname: Leung
authors.forename: Lim Kwong
authors.initials: LK
authors.lastname: Cheung
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D016022:Case-Control Studies; D002680:Chin / Q000294:innervation; D015331:Cohort Studies; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007431:Intraoperative Complications; D008046:Lip / Q000294:innervation; D008297:Male; D008334:Mandible / Q000000981:diagnostic imaging / Q000294:innervation / Q000601:surgery; D008340:Mandibular Nerve / Q000000981:diagnostic imaging; D008875:Middle Aged; D008964:Molar, Third / Q000000981:diagnostic imaging / Q000601:surgery*; D017288:Pain Threshold / Q000502:physiology; D011183:Postoperative Complications; D011446:Prospective Studies; D011862:Radiography, Panoramic; D012307:Risk Factors; D012684:Sensory Thresholds / Q000502:physiology; D014081:Tooth Extraction; D014092:Tooth Root / Q000000981:diagnostic imaging; D020390:Tooth Socket / Q000294:innervation / Q000473:pathology; D014095:Tooth, Impacted / Q000000981:diagnostic imaging / Q000601:surgery; D014110:Touch / Q000502:physiology; D016896:Treatment Outcome; D061221:Trigeminal Nerve Injuries; D055815:Young Adult